Adding mix shaders and glossy shaders
Yes, the point is to add additional reflection components without combining their reflected energy, which would make the surface appear to glow. Is it helping? Maybe, maybe not. Carpaint shading is usually less complicated than a lot of people make it out to be. People have a habit of getting carried away with a lot of crazy effects with drag down rendering time and only even look good under one specific lighting setup.

I honestly have no idea what the artist was trying to do in that first screenshot, and I'm not sure they did either. Fresnel node with IOR=1 outputs solid black, so a bunch of the nodes on the bottom of the image aren't even doing anything.

The second one is decent enough carpaint, just inefficient in some ways. The two mix diffuse shaders could be subsituted by mixing colors with the mixRGB node and passing it to a single shader. The voronoi texture is there to make the sparkly flakes seen in some car paints. (note: most modern metallic paints have very small and dense flakes that are better approximated with a rough glossy shader than trying to represent them directly with a texture).